Labour leader's name booed as he is branded a disgrace at a public sector unions' rally in London

The scene outside Methodist Central Hall in Westminster, where a rally was held and Ed Miliband's name was booed for his criticism of the strike by public sector unions. Photograph: David Levene for the Guardian
David Levene/Guardian

Labour leader Ed Miliband denounced the strike by public sector workers for the third time in six days, saying it was a mistake, wrong and would not help them win the argument.

Miliband's name was booed and he was branded a disgrace at a union rally in London, while the TUC general secretary Brendan Barber was also highly critical. One of many dissenting Labour blogs suggested Miliband's performance in a BBC interview had been reminiscent of a hostage video.

But his office insisted it was not good politics to be seen to take industrial action before negotiations had been exhausted. Miliband chose a long-arranged speech to the Local Government Association to urge unions to think again how to wage the battle for public opinion, especially if the strikes are going to build through the autumn.

Miliband said bluntly: "I believe this action is wrong. Negotiations are ongoing. So it is a mistake to go on strike because of the effect on the people who rely upon these services. And it is mistake because it will not help to win the argument. The Labour party I lead will always be the party of the mums and dads who know the value of a day's education."

For a man portrayed by the Conservative party as the unions' squeeze, this was stark stuff. But Miliband has some short-term latitude because the unions on strike yesterday are not institutionally affiliated to the Labour Party. "We are not going to hitch our star to [PCS general secretary] Mark Serwotka," said one shadow cabinet member. Miliband knows he will face a sharper political dilemma if the other big public sector unions, Unison and Unite – Labour's chief donors – join the action in the autumn.

Miliband respects both the Unison general secretary Dave Prentis and Barber, and will press both men to ensure any autumn strikes do not look like a defence of privilege and public sector largesse.

Shadow cabinet members have a different view of the Unite general secretary, Len McCluskey, who they think has vacated the stage partly in an attempt to engineer a takeover of the PCS.

Cabinet members, meanwhile, have struggled to make the intellectual case for the reduction in public sector pensions. Justine Greening, the Treasury minister, had floundered on Wednesday's BBC radio 4 Today programme when it was pointed out that Lord Hutton's report showed public sector pensions as a proportion of GDP were already projected to decline. The Hutton tables show the percentage of spending as a share of GDP falling from 1.9% now to 1.4% in 2050.

Remarkably, on the same programme 24 hours later, Cabinet Office minister Francis Maude seemed totally unprepared for the same line of questioning, and also fell apart. It was only by mid-afternoon that the government had reassembled a case. "That is what happens when George Osborne spends a day in the Royal Box at Wimbledon," said one shadow cabinet member.

Miliband is also trying to use the strike to make a wider argument that the coalition is socially divisive on the deficit, seeking to turn parents against teachers, and the public against public sector workers.

When Labour was in government, he argued, it engineered big changes in public sector pensions "without strike action". Similarly, unions under a Labour government had taken pay cuts to prevent the recession turning into an era of mass unemployment. Miliband said: "The government has gone about making that change happen in exactly the wrong way, announcing a 3% surcharge on public sector workers before John Hutton had even published his report, then announcing their final position when negotiations were still going on.

"What the British people want and expect is that you now get back to the negotiating table and redouble your efforts to find an agreed solution."

It is a delicate balance for Miliband. If he can sound like an independent voice of reason, not in hock to the unions, he benefits. But if the unions and the government get locked in a major confrontation, he could find himself as the much-discussed squeezed middle.